Base assembly for swivel lamp

ABSTRACT

This lamp base assembly includes an exterior housing pivotally mounted to a wall bracket, and an interior housing pivotally mounting an extensible arm to the exterior housing. A torsion spring, attached at one end to the exterior housing and at the other end to the interior housing, provides a resistance torque balancing the arm at a predetermined position. An adjustable brake shoe assembly mounted to the exterior housing and engageable with the interior housing provides the friction force necessary to compensate for imbalance of the arm at other positions.

United States Patent 1 1 Rogers BASE ASSEMBLY FOR SWIVEL LAMP [75] Inventor: Gerald L. Rogers, St. Louis, Mo.

[73] Assignee: Chemetron Corporation, Chicago,

Ill.

[22 Filed: May7, 1973 21 Appl. No; 357,729

[52] US. Cl 248/279, 248/280, 403/91, 403/120 [51] Int. Cl. Fl6m 13/00 [58] Field of Search 248/123, 279, 281, 292, 248/296, 324; 403/91, 120; 240/73 BI [56] v References Cited UNITED STATES PATENTS 8/1920 Runkel 248/324 Trythall 248/123 [111 3,823,906 [451 July 16, 1974 2,299,251 10/1942 Perla] 248/280 2,395,178 2/1946 Fiori 248/280 3,003,737 10/1961 Mehr 248/280 X Primary Examiner-William H. Schultz 5 7] ABSTRACT This lamp base assembly includes an exterior housing pivotally mounted to a wall bracket, and an interior housing pivotally mounting an extensible armto the exterior housing. A torsion spring, attached at one end to the exterior housing and at the other end to the interior housing, provides a resistance torque balancing the arm at a predetermined position. An adjustable brake shoe assembly mounted to the exterior housing and engageable with the interior housing provides the friction force necessary to compensatefor imbalance of the arm at other positions.

10 Claims, 6 Drawing Figures 9 PATENTEI] JUL 1 6 I974 SHEET 1 BF 2 1 BASE ASSEMBLY FOR SWIVEL LAMP BACKGROUND OF THE INVENTION:

This invention relates to a base assembly for a swivel lamp having an elongate arm, and particularly to a base assembly having a frictionally controlled, torsion spring balance.

Lamp assemblies, which have as their object the holding of the lamp in a stable condition in all adjusted positions, are well known in the prior art and in lamp assemblies that include an extensible arm, which is rotatable about a base assembly, it is necessary to provide some means of balancing the increase in the gravity moment which results when the center of gravity of the lamp structure moves outwardly from the center of rotation,.as the lamp is moved to a new position.

It is, of course, possible and relatively simple to provide a friction joint between an extensible arm and the base to which it is connected which will resist a variable turning moment at all lamp positions. However, this solution is impractical for the obvious reason that an arm held by friction at its outermost extension portion would require considerable force to move it in the innermost retraction range.

In general, therefore, the balance means of most known swivel lamps is provided, at least in part, by either a spring or acounterweight. When a counterweight is used the theoretical requirement for perfect balance is that the counterweight must move away from the pivot center in exact proportion to the outward movement of the center of gravity. If a spring is used some means must be provided for varying the spring loading to compensate for the increased imbalance as the center of gravity moves outward. One way of approaching the problem is to provide relatively complex parallel arm systems. However, such systems in practice do not achieve sufficiently-good balance at all positions and friction joints are invariably provided to overcome the loading differential which occurs.

Unfortunately, in addition to this disadvantage, parallel arm structures tend to be rather complicated and consequently expensive to manufacture particularly when the extension range is greater than 1 or 2 feet. Further, such systems are not readily adaptable to arms which are extensible by telescopic means.

The present assembly overcomes these and other deficiencies in a manner not revealed by the known prior art.

SUMMARY OF THE INVENTION:

, pensate for the maximum differential turning moment,

resulting from the gravity load and the torsion spring, and hold the lamp in any position within a chosen range.

The torsion spring may be preloaded so that the arm is disposed in a desired angular position at a desired extension in a free balance condition in which the gravity moment and spring torque are equal.

The lamp assembly is relatively inexpensive to construct, simple to operate and install and easy to operate by fingertip control and is particularly suitable for use in hospital rooms and the like, for examination purposes as well as reading purposes.

It is an important object of this invention to provide a lamp base assembly having an exterior housing; an interior housing rotatably mounted within the exterior housing; an elongate arm attachedto and rotatable with said interior housing; a torsion spring resisting angular movement of the arm under gravity; and adjustable friction means to compensate for the netturning moment resulting from the gravity moment and the spring torque and hold'the arm in any position within a givenrange.

It is'an important object to provide a torsion spring which is housed within the interior housing and connected between the interior and exterior housings.

It is another important object to provide friction means which includes a brake shoe mounted in adjustable relation to the exterior housing for pivotal and translational movement.

It is another object to provide a substantially cylindrical interior housing having ametal band embracingly disposed about its outer face to provide a brake drum face engageable by the brake shoe.

A further object of the invention is to provide an adaptor attaching the arm to the interior housing, the adaptor including clamping means attaching the metal band ends to the interior housing.

Yet another important object is to provide the brake shoe with a slot and pin mounting to the exterior housing at one end, and to provide bearing means at the other end of the brake shoe engageable by an adjustment screw mounted to the exterior housing to permit the brake shoe lining to move circumferentially about the metal hand during pressure adjustment thereby facilitating even pressure distribution.

Another object of the invention is to provide an adjustment screw having a bearing shoulder and a reduced portion, and to provide the brake shoe with an opening receiving said screw, the opening being config-. urated to provide a bearing face for a spring means disposed between the screw and the shoe.

Another important object of the invention is to provide an extensible elongate arm and to preload the torsion spring so that at a selected extension anda se-' lected angular position of the elongate arm below the horizontal, the arm is balanced without assistance from the friction means, and to provide a brake friction capability sufficient to hold the arm in any other position within the extension and the angular movement range.

BRIEF DESCRIPTION OF THE-DRAWINGS:

FIG. 1 is an elevational view of the lamp assembly;

FIG. 2'is a view from the underside of the lamp assembly showing the base assembly partly in cross sec tion;

FIG. 3 is a cross sectional view taken on line 3-3 of taken on FIG. 6 is a graphic representation of spring load and gravity load conditions at various angular positions of the arm.

DESCRIPTION OF THE PREFERRED EMBODIMENT:

stored in a lamp receiver structure which overfits a wall-mounted channel 16.

Turning now more specifically to the base assembly 10 it will be understood that this assembly includes an exterior housing 20, which is pivotally mounted about a vertical axis to the wall bracket 14 by means of upper and lower hinge pins 21 and 22. The exterior housing includes decorator covers 23 and 24 on opposite sides.

The telescopic arm 11, which constitutes an extensible arm, is provided with pivotal movement about a horizontal axis by means of attachment toa substantially cylindrical interior housing 25, which is pivotally mounted between the side walls 26 and 27 of the exterior housing by means of a horizontal shaft 30. An adaptor member 31 provides the attachment means between the telescopic arm 11 and the interior housing 25. The angular rotation of the interior housing and hence of the arm 11 .is resisted by a torsion spring 40 mounted within the interior housing 25 and attached between the exterior housing 20 and said interior housing 25. As will be explained, imbalance between gravity force acting on the arm 11 and the resisting force provided by the spring 40, is controlled by means of an adjustable brake shoe assembly generally indicated by numeral 32. The structural relationship of the housings 20 and 25, the torsion spring 40 and the brake shoe assembly 32 is best understood by reference to FIGS. 3 and 4 The interior housing 25, in effect provides a brake drum and in the preferred embodiment comprises essentially an integral inner member of plastic material having an outer cylindrical wall 33, which is provided with a plurality of inwardly projecting reinforcing elements 34; a cylindrical inner wall 35, and a connecting annular wall 36. The cylindrical inner wall 35 provides a journal mounting receiving the shaft 30, which is disposed in fixed rotatable relation to the exterior housing side walls 26 and 27. The cavity between the inner and outer cylindrical side walls 33 and 35 provides a housing for the torsion spring and a cylindrical spacer 41.

As best shown in FIG. 2, the torsion spring 40 includes opposed ends 42 and 43 which arereceived within apertures 44 and 45 provided in the exterior housing side wall 26 and the interior housing annular wall 36 respectively. It will be understood that this'connection provides the interior housing 25, and therefore the telescopic arm 11, with a torsion spring resistance to rotation about the shaft 30 as is best illustrated in FIG. 4. The interior housing 25 includes an outer band 46 of stainless steel, or similar material of relatively small frictional resistance. The band 46 is provided with opposed ends 47 by which it is attached in clamped relation to the interior housing 25. The band ends 47 are clamped to the interior housing 25 by means of the adaptor means 31 to which the telescopic arm 11 is connected. To this end the interior housing 25 includes a pair of spaced notched portions 50 and the adaptor 31 includes a body-portion '51 and a pair of spaced arms 52 having beveled ends 53, which are received into notched portions 50 to clamp the band ends 47 securely in place when the adaptor member 3l is connected to said interior housing25, said connection being accomplished by means of a threaded fastener 54. lt will be understood that the adaptor member 31 includes an axial aperture 55 receiving the fastener 54 therethrough and that the interior housing 25 includes a fixed threaded insert 56 to which said threaded fastener 54 is connected. The adaptor body portion 51 in the preferred embodiments includes slotted sides to facilitate the fitting of the tubular telescopic arm 11.

Turning now to the brake shoe assembly 32, and with particular reference to'FIGS. 3 and 4, itwill be understood that this assembly includes a brake shoe 60 having a lining 6l of Teflon or similar material attached thereto, said lining being compatibly arcuately formed to engage the outer metal band 46 of the interior housing 25. The brake shoe 60 includes a slot 62 at one end and is mounted to the exterior housing 20 by means of a shaft 63 which extends between the exterior housing sidewalls 26 and 27 and is received by said slot 62. The exterior housing upper sidewall 28 is provided with an internally threaded insert 64, which receives an adjustment screw 65, constituting an extensible means and having a reduced diameter end 66 defined by a shoulder 67. The associated end of the brake shoe 60 is provided with an opening 70 having an upper portion 7] and a reduced diameter lower portion 72 defined by a bearing margin 73. The diameter of the upper portion 71 is sufficiently great to provide diametrical clearance for a plurality of belleville spring washers 74, which receive the reduced end 66 of the adjustment screw 65. The opening lower portion 72 is of a size to provide diametric clearance for said reduced end 66 and pressure applied by the screw bearing shoulder'67 is transferred to the bearing engagement area in the vicinity of the bearing margin 73. Because of this arrangement the brake shoe 60 can be moved translationallyas it is pivoted about the shaft 63. Thus, when pressure is applied to the brake shoe 60 by means of the adjustment screw v65 the lining 61 is permitted to move circumferentially about the metal band 46, which ensures an even distribution of friction pressure between the brake shoe lining 61 and the brake drum band 46. This movement is not great but is sufficient to ensure that excessive and therefore uneven pressure does not occur on the edge of the brake shoe lining 61 farthest from the shaft 63. In the preferred embodiment, the range of angular movement of the telescopic arm 11 is from an upper position slightly above horizontal to a lower position determined by the location of stop 75 as shown in FIG. 4

It will be understood that the weight of the lamp head 12 and the telescopic arm 11 tend to rotate the interior housing in a clockwise direction against the resistance of the torsion spring 40. The torsion spring can be chosen so that a balance between the gravity moment of the arm and the torque resistance of the spring occurs at a selected angular position of the arm 11. When an optimum balance position is achieved, for example when the arm 11 is at a selected extension and at a selected angle as shown in FIG. 5, the spring torque and the gravity moment are equal as shown in FIG. 6, it being understood that the gravity moment for an arm of a selected length is a function of the cosine of the angle of elevation alpha, and that the spring torque is a function of the angle of twist, which is also alpha. By choosing a suitable equalization or free balance position the brake friction can be adjusted to ensure that when the arm is disposed on either side of this balance position it is maintained in position. i

It is thought that the structural features and functional advantages of this lamp base assembly have become fully apparent from the foregoing description of parts but for completeness of disclosure the operation of the device will be briefly described.

It will be understood that the lamp is stored in its fully telescoped position asshown in FIG. 1, and that it must be swung outwardly of the wall receiver about the vertical pivot axis of the wall bracket 14 before the telescopic, arm can be extended or rotated to a desired angle of elevation. As will be clearly understood from FIG. 5 the weight of the lamp assembly as a whole tends to rotate the arm 11 in a clockwise direction. For any selected extension ofthe telescopic arm 11, the gravity moment varies as the cosine of the angle alpha. This gravity moment is at a maximum for a particular extension when the lamp is farthest from the pivot center of the shaft 30, which occurs when the telescopic arm is horizontal. In the preferred embodiment the torsion spring 40 is preloaded so that there is a tendency for said spring to exert a counterclockwise torque on the arm 11 when the arm is horizontal. The preloading is chosen so that the torque equalizes the gravity moment at an-angle between the horizontal and lower angular range of the arm 11 which, in the preferred embodiment, is about 60 below horizontal. The advantage of preloading the torsion spring is that there is proportionately less torque variation over the working range of angular movement. In .the preferred embodiment the arm 11 is freely balanced when the arm is fully withdrawn as shown in FIG. 5. It will be understood that if the arm 11 is raised to the horizontal and released it will tend to return to its balance position under gravity and that likewise if the arm is lowered below the balance position against the resistance of the torsion spring and released it will return upwardly to its balance position. By applying a sufficient frictional brake force to the interior housing 25, by means of the adjustable brake assembly 32, to compensate for this tendency to return to the free balance position, the arm 11 can be held at any intermediate angular elevation.

If the arm 11 were of a fixed length, adjustment of the friction to overcome the greater of the spring force and the gravity force, tending to return the arm of its free balance position, would permit the arm to be disposed in any position within the angular range with a minimum of applied load. However, it will be understood that when the arm is extended, the gravity moment is increased. The friction must therefore be adjusted to ensure that it is sufficient to overcome the maximum moment differential, taking into consideration the -exhold the lamp in anyposition .within the combined chosen range.

I claim as my invention: 1. In a lamp base assembly: a. an exterior housing, b. shaft means mounted to the exterior housing, c. an interior housing mounted on the shaft means in rotatable relation to the exterior housing and including an arcuate face,

d. an elongate arm extending outwardly from said ex- 7 terior housing,

e. attachment means attaching said elongate arm to said interior housing,

f. spring means including a torsion spring mounted on the shaft means and having opposed ends, one of said ends being attached to the exterior housing and the other of said ends being attached to the interior housing, whereby said torsion spring resists angular movement of the arm under gravity, and g. friction means carried by the exterior housing and including:

1. brake shoe means having an arcuate face engageable with the arcuate face of the interior housing to resist angular movement of the arm in either direction, and

2. adjustment means selectively applying pressur to said brake shoe means to at least balance the net turning moment resulting from the action of the torsion spring and gravity'when the arm is moved to a selected position so that said arm 3. A lamp base assembly as defined in claim 1, in

which:

h. the brake shoe means includes a body portion and a lining portion attached to said body portion and providing the arcuate face engageable with said interior housing, and

. the adjustment means includes pivot means attaching said body portion to said exterior housing and pressure means selectively applying a force to said body portion in spaced relation from said pivot means to increase or decrease the frictional engagement of the lining portion with the interior housing.

.4. A lamp base assembly as defined in claim 3, in

which:

j. the pivot means includes a slot and a pin received within said slot for translational movement of the body portion, and

k. The pressure means includes a threadedly extensible' means disposed between said exterior housing and said body portion to selectively move said body portion about the pivot center. 5. A lamp base assembly as defined in claim 4, in which:

l. the exterior housing includes a portion engageable with the extensible means,

m. the body portion includes a portion engageable with the extensible means, and g 11. one of said engageable portions is threadedly related to said extensible means and the other of said portions is bearingly related to said extensible means whereby relative rotation of said extensible means selectively separates said portions.

6. A lamp base assembly as defined in claim 5, in

which:

0. the extensible means includes a threaded element having a bearing shoulder and a reduced diameter portion,

p. said bearingly related engagement portion includes an aperture, receiving said element reduced diameter portion, and a bearing margin,

q. a spring washer is disposed between said element bearing shoulder and the bearing margin of said bearingly related engagement portion, and

r. said element reduced diameter portion is movable within said aperture to permit translational movement of the body portion of said brake shoe means relative to said exterior housing to permit the arcuate lining of said brake shoe means to slide relative to said interior housing and facilitate even pressure distribution of said lining on said interior housing.

7. A lamp base assembly as defined in claim 2, in

which:

j. the interior housing inner portion includes a pair of spaced, substantially radially disposed shoulder portions,

k. said band ends are substantially radially disposed to engage said radially disposed shoulder portions,

1. said attachment means includes:

1. an adaptor having a radially disposed tubular portion at one end receiving said extensible arm and a pair of spaced clamping portions at the other end, each clamping portion including a radial face engageable with said band ends, and

2. fastener means interconnecting said adaptor to said interior housing inner portion to draw the spaced clamping portions into engagement with said band ends.

8. A lamp base assembly as defined in claim 1, in

which:

h. the torsion spring is preloaded so that at a selected angular position of the extensible arm below the horizontal the spring torque balances the gravity moment of the arm.

9. A lamp base assembly as defined in claim 1, in

which:

h. the elongate arm is extensible,

i. the torsion spring is preloaded so that at a selected extension of said arm and a selected angular position of said arm below substantially the horizontal,

said arm is balanced without assistance from the friction means and when the arm is moved upwardly it is returned to the balance position under gravity and when the arm is moved downwardly it is returned to the balance position under spring load,and the applied frictional torque is sufficient 2. an outer metal band conforming to said arcuate face and including opposed ends, d. an elongate arm extending outwardly from said exterior housing in extensible relation,

e. attachment means attaching said elongate arm to said interior housing including:

1. an adaptor having a tubular portion at one end receiving said arm and spaced clamping portions at the other end clamping the metal band ends to the inner portion of the interior housing, and

2. fastener means attaching the adaptor to the inner portion of the interior housing,

f. spring means including a torsion spring mounted-on the shaft means and having opposed ends, one of said ends being attached to the exterior housing and the other of said ends being attached to the interior housing, whereby said torsion spring resists angular movement of the arm under gravity,

g. brake shoe means, including:

' l. a body portion having a slot at one end and a bearing socket at the other end,

2. a lining portion attached to the body portion between the ends thereof and having an arcuate face pressure engageable with the metal band, and

Y h. adjustment means, including:

1. a pivot pin attached to the exterior housing and received by the body portion slot,

2. an extensible element threadedly connected to the exterior housing and receivable within the bearing socket at the other end, and

3. a spring washer disposed within the bearing socket of the body portion and engageable by the extensible element, whereby-extension of the element induces rotational and translational movement into the body portion to increase or decrease the pressure between the brake shoe lin ing portion and the metal band to balance the net turning moment resulting from the action of the torsion spring and gravity when the arm is moved to a selected position so that the arm maintains that position. 

1. In a lamp base assembly: a. an exterior housing, b. shaft means mounted to the exterior housing, c. an interior housing mounted on the shaft means in rotatable relation to the exterior housing and including an arcuate face, d. an elongate arm extending outwardly from said exterior housing, e. attachment means attaching said elongate arm to said interior housing, f. spring means including a torsion spring mounted on the shaft means and having opposed ends, one of said ends being attached to the exterior housing and the other of said ends being attached to the interior housing, whereby said torsion spring resists angular movement of the arm under gravity, and g. friction means carried by the exterior housing and including:
 1. brake shoe means having an arcuate face engageable with the arcuate face of the interior housing to resist angular movement of the arm in either direction, and
 2. adjustment means selectively applying pressure to said brake shoe means to at least balance the net turning moment resulting from the action of the torsion spring and gravity when the arm is moved to a selected position so that said arm maintains that position.
 2. A lamp base assembly as defined in claim 1, in which: h. the interior housing includes an inner portion having an arcuate face of substantially constant radius and an outer metal band disposed about said arcuate face and engageable by said shoe, said band including opposed ends, and i. the attachment means attaching the arm to the interior housing includes clamping means attaching said metal band ends to said inner housing portion.
 2. adjustment means selectively applying pressure to said brake shoe means to at least balance the net turning moment resulting from the action of the torsion spring and gravity when the arm is moved to a selected position so that said arm maintains that position.
 2. an extensible element threadedly connected to the exterior housing and receivable within the bearing socket at the other end, and
 2. a lining portion attached to the body portion between the ends thereof and having an arcuate face pressure engageable with the metal band, and h. adjustment means, including:
 2. fastener means attaching the adaptor to the inner portion of the interior housing, f. spring means including a torsion spring mounted on the shaft means and having opposed ends, one of said ends being attached to the exterior housing and the other of said ends being attached to the interior housing, whereby said torsion spring resists angular movement of the arm under gravity, g. brake shoe means, including:
 2. an outer metal band conforming to said arcuate face and including opposed ends, d. an elongate arm extending outwardly from said exterior housing in extensible relation, e. attachment means attaching said elongate arm to said interior housing including:
 2. fastener means interconnecting said adaptor to said interior housing inner portion to draw the spaced clamping portions into engagement with said band ends.
 3. a spring washer disposed within the bearing socket of the body portion and engageable by the extensible element, whereby extension of the element induces rotational and translational movement into the body portion to increase or decrease the pressure between the brake shoe lining portion and the metal band to balance the net turning moment resulting from the action of the torsion spring and gravity when the arm is moved to a selected position so that the arm maintains that position.
 3. A lamp base assembly as defined in claim 1, in which: h. the brake shoe means includes a body portion and a lining portion attached to said body portion and providing the arcuate face engageable with said interior housing, and i. the adjustment means includes pivot means attaching said body portion to said exterior housing and pressure means selectively applying a force to said body portion in spaced relation from said pivot means to increase or decrease the frictional engagement of the lining portion with the interior housing.
 4. A lamp base assembly as defined in claim 3, in which: j. the pivot means includes a slot and a pin received within said slot for translational movement of the body portion, and k. The pressure means includes a threadedly extensible means disposed between said exterior housing and said body portion to selectively move said body portion about the pivot center.
 5. A lamp base assembly as defined in claim 4, in which: l. the exterior housing includes a portion engageable with the extensible means, m. the body portion includes a portion engageable with the extensible means, and n. one of said engageable portions is threadedly related to said extensible means and the other of said portions is bearingly related to said extensible means whereby relative rotation of said extensible means selectively separates said portions.
 6. A lamp base assembly as defined in claim 5, in which: o. the extensible means includes a threaded element having a bearing shoulder and a reduced diameter portion, p. said bearingly related engagement portion includes an aperture, receiving said element reduced diameter portion, and a bearing margin, q. a spring washer is disposed between said element bearing shoulder and the bearing margin of said bearingly related engagement portion, and r. said element reduced diameter portion is movable within said aperture to permit translational movement of the body portion of said brake shoe means relative to said exterior housing to permit the arcuate lining of said brake shoe means to slide relative to said interior housing and facilitate even pressure distribution of said lining on said interior housing.
 7. A lamp base assembly as defined in claim 2, in which: j. the interior housing inner portion includes a pair of spaced, substantially radially disposed shoulder portions, k. said band ends are substantially radially disposed to engage said radially disposed shoulder portions, l. said attachment means includes:
 8. A lamp base assembly as defined in claim 1, in which: h. the torsion spring is preloaded so that at a selected angular position of the extensible arm below the horizontal the spring torque balances the gravity moment of the arm.
 9. A lamp base assembly as defined in claim 1, in which: h. the elongate arm is extensible, i. the torsion spring is preloaded so that at a selected extension of said arm and a selected angular position of said arm below substantially the horizontal, said arm is balanced without assistance from the friction means and when the arm is moved upwardly it is returned to the balance position under gravity and when the arm is moved downwardly it is returned to the balance position under spring load, and the applied frictional torque is sufficient to hold the arm in any position within the extension range and the angular movement range.
 10. In a lamp base assembly: a. an exterior housing, b. shaft means mounted to the exterior housing, c. an interior housing mounted to the shaft means in rotatable relation to the exterior housing and including: 